import numpy as np
n=10
result = 0
a = [False for _ in range(n)]
if n > 2:
    result = result + 1

for i in range(3, n, 2):
    if not a[i]:
        result = result + 1
        j = 3
        while i * j < n:
            a[i * j] = True
            j = j + 2
print(result)
